Tuesday's 3.5 magnitude earthquake that shook Dyersburg and parts of northwest Tennessee may have been unwelcome, coming in conjunction with several inches of snow, but it wasn't really a cause for concern, a local quake watcher said Wednesday.

Gary Patterson, a geologist and director of the Center for Earthquake Research and Information at the University of Memphis, said 38 quakes of roughly that strength -- magnitude 3.6 or higher -- have been recorded in the New Madrid seismic zone since 1974.

"So almost one per year on average," Patterson said.

He said a quake of about that magnitude might knock over some unsecured furniture but wasn't likely to cause damage to any well-constructed building.

The largest quake CERI has recorded in the New Madrid zone was a magnitude 5.0 on March 25, 1976, that caused minor architectural damage in Memphis, Patterson said.

The City of Dyersburg noted the Tuesday quake, centered near Caruthersville, Mo., on its Facebook page, and many people commented that they felt it.

Patterson said the frequency of earthquakes in the zone has increased 20-30 percent since 2015.

"We're not sure what to make of it right now," he said, "but we don't see it as normal behavior. We don't know enough about it to really make a definitive statement. It's still within the standard deviation, so we can't say a whole lot."

Added Patterson: "There's a 25-40 percent chance of a magnitude 6.0 or greater in a 50-year window, but the chances of the 'big one' are pretty slim, about 1 in 500."